Chainstays are important members of the rear triangle structure of a bicycle. Not only are they significant load carrying members but their overall geometry plays an important role in the riding and handling characteristics of the bicycle system. Generally speaking, the goal of the competition bicycle designer is to minimize the length of the chainstay while maximizing the tire and chain-ring clearances. Generally these are two very conflicting goals.
Minimizing the length of the chainstay benefits the bicycle in two respects. First, it gives the bicycle a quicker steering response. This is important in competition riding. Second, it improves the traction of the rear tire. It accomplishes this by placing more of the riders weight over the rear tire. It also causes a greater portion of the pedal forces to be reacted by the rear axle, since the pedals are also moved closer to the rear axle. The improved traction is important in hard sprint and climbing maneuvers.
Maximizing the tire and chain-ring clearances are especially important for mountain bicycles. Because of the environment in which these bicycles are ridden and the oversized tires they generally use (with their pronounced tread), more clearance is needed to handle mud and other debris clinging to the tire tread.
Current production bicycles generally have reached the best possible compromise between the length of the chainstay and the tire and chain-ring clearances. A larger diameter of the chainstay is beneficial to provide lightweight bending and torsional stiffness, and to support the high loads placed upon the chainstays, from the rear wheel, bottom bracket and imposed chain loads. Typically chainstays are bent, dented or crimped to provide some degree of tire and chainring clearance. The dented or crimped chainstays appear to lose substantial strength as a result. There is not much more that can be achieved using the prior art production methods. However, with this invention the limitations and restrictions of the past have been diminished and it is now possible to pack a more efficient, higher strength structure in a smaller space to allow both shorter chainstays and more tire and chain-ring clearances than possible before.